Dark energy stands as one of the biggest mysteries in modern cosmology. Since 1998, we have known the expansion rate of the Universe is increasing, but have had no idea what is causing this acceleration. "Dark energy" is merely the name we give our ignorance. However, a new instrument called the Dark Energy Camera (DECam) may help measure many of the properties of cosmic acceleration, including whether it has always been present in the Universe, or if its effects evolved over time.

DECam on the Victor M. Blanco telescope. The camera itself is the black cylinder at the image center. Light from distant galaxies is focused by the 4-meter-diameter mirror at left into the camera.

DECam is mounted on the Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile, where dark energy was first observed in 1998. As the name indicates, it is a camera, albeit a far more sensitive one than is available to consumers. The business end of the camera is a set of 62 charged-coupled devices (CCDs), yielding images of 570 megapixels. Unlike the CCDs present in ordinary digital cameras, those in DECam are sensitive to extremely low light levels, and it can image well into infrared wavelengths, thanks to a new detector design developed at Lawrence Berkeley National Laboratory. The largest lens on DECam is 98 cm in diameter and weighs 380 pounds (only slightly smaller than the lens on the Yerkes Observatory, which still holds the record at 102 cm).

The first images from DECam were released yesterday, and focused on many familiar astronomical objects to ensure the equipment was operating properly. Over the next 5 years, DECam will image approximately 1/8 of the entire sky as part of the Dark Energy Survey (DES), taking high-resolution pictures of roughly 300 million galaxies. The survey should discover an estimated 4000 supernova explosions, which can be used to measure the acceleration of the Universe to greater precision than ever before.

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A celebration of Cassini

A celebration of Cassini

A celebration of Cassini

Nearly 20 years ago, the Cassini-Huygens mission was launched and the spacecraft has spent the last 13 years orbiting Saturn. Cassini burned up in Saturn's atmosphere, and left an amazing legacy.